In the prior art, processes for marking polymeric materials are known. Materials of this type comprise a radiation-sensitive additive which causes a color change in the material on exposure to radiation in certain wavelength ranges. These additives are known as laser pigments.
The prior art also discloses polyolefin films which are biaxially oriented for certain applications and generally have a thickness in the range from 3 to 100 μm. It is known to modify biaxially oriented films by means of suitable additives. Additives of this type can improve the friction, the antistatic properties, the thermal stability, the appearance or other film properties. However, these additives must not have an excessively adverse effect on other important service properties.
The object of the present invention was to provide a laser-markable polyolefin film. In particular, the film should be markable with laser light by means of suitable processes. The laser mask should have good contrast, and should preferably appear as a dark mark. During marking, holes through the film must not be produced by the laser beam. At the same time, the film should have a good appearance and good service properties.